1. Field of the Invention
The present invention relates to a method of converting storage pumps into reversible pump-turbines.
2. Description of the Related Art
Pumps are used to pump up water from a low position to a high position. Such a pump has an impeller runner, which is rotated by an electric motor, thereby pumping up water. On the other hand, in places where there is a demand for pumping-up of water, it is also demanded to drop water from a high position to a low position in many cases. In those cases, water is generally naturally dropped by gravity while bypassing the pump. In that connection, there has arisen a demand for more effective utilization of energy through power generation utilizing the head. This demand means that the pump is rotated in the reversed direction to serve as a power generator.
It is sure that an impeller runner rotated to function as a pump can be rotated in the reversed direction. However, because the impeller runner is not originally designed on the premise that it serves also as a pump-turbine, the impeller runner has poor performance when it is employed as a turbine, and satisfactory power generation cannot be essentially achieved.
In view of the state of the art set forth above, it is an object of the present invention to provide a method of converting storage pumps into reversible pump-turbines, which can perform effective power generation.
To achieve the above object, the present invention provides a method of converting a storage pump into a reversible pump-turbine, the method comprising the steps of dismounting, from the storage pump which pumps up water to a water conduit by rotating an impeller runner in a scroll case with a rotary electric machine, said impeller runner; replacing or adapting the impeller runner with or to a runner having a smaller outer diameter than said impeller runner; providing vanes in positions closer to the scroll case side than a position where the replaced or adapted runner is disposed; and modifying the rotary electric machine or rotation control thereof such that a rotational speed of the replaced or adapted runner is increased from a rotational speed before the replacement or adaptation, when the replaced or adapted runner is rotated for power generation based on the head of the water conduit.
Also, the present invention provides a method of converting a storage pump into a reversible pump-turbine, the method comprising the steps of dismounting, from the storage pump which pumps up water to a water conduit by rotating an impeller runner surrounded by a head cover and a bottom cover in a scroll case under control with a rotary electric machine, the head cover or the bottom cover; and adapting at least a portion of the impeller runner near an outer periphery thereof such that an angle of the portion measured relative to a circumferential direction is reduced.
According the present invention thus constructed, storage pumps can be converted into reversible pump-turbines capable of being satisfactorily put into practical use.